I connected my computer to a domain , but now when I start the computer the screen pops up and ask for username and password and then it shows the domain name

I connected my computer to a domain , but now when I start the computer the screen pops up and ask for username and password and then it shows the domain name.
I no longer want to log on the domain but to my regular computer. I change the bottom part to (ITIS) This computer ---but it still ask for a username and password when I did not have one from before. How do I get back to my local c drive?

Then someone told me to go to --> my computer--> computername and change it to workgroup I named it Jim
and then restarted.
It asked for username and password again. I did not enter a username or password for it.
Now I can not get to domain, workgroup, or local c drive. Please help as soon as possable.


Thanks.